Brief Articles
Journal of Medicinal Chemistry, 2007, Vol. 50, No. 20 5037
mixture of 2,4-dichloroaniline (20.9 g, 0.16 mol), 37% HCl (39
mL), and water (39 mL). Sodium acetate trihydrate (18.2 g, 0.22
mol) was added while stirring on an ice bath for 20 min. This
mixture was added to an ice-cooled and well-stirred solution of
ethyl 2-methylacetoacetate (90%, 25.6 g, 0.162 mol) and potassium
acetate (31.7 g, 0.32 mol) in methanol (157 mL). The mixture was
stirred at 0 °C for 3 h and then extracted with diethyl ether. The
organic layer was separated, washed with brine, and dried.
Evaporation of the solvent gave a residue that was dissolved in
ethanol (250 mL) and stirred at room temperature for 3 days. The
resulting suspension was cooled at 4 °C overnight and filtered to
give compound 18 as crystals (11.8 g, 27%), mp 118-120 °C (from
substitution in terms of drug resistance, as we previously
characterized in our laboratory from an enzymological point of
view.
Conclusions
The dihalo-IASs showed potent antiviral activity and were
not cytotoxic up to 20 000 nM. The 4,5-difluoro- (10) and
5-chloro-4-fluoro (16) derivatives were the most potent inhibi-
tors of HIV-1 WT (ED50 ) 1 and 0.5 nM, respectively, in MT-4
cells) and the Y181C and K103N-Y181C NNRTI-resistant
strains. These potent derivatives were characterized by the
presence of a fluorine atom at position 4 of the indole nucleus.
Compounds 10 and 16 were highly effective against the 112
and the AB1 strains in lymphocytes and inhibited at nanomolar
concentration the multiplication of the IIIBBa-L strain in mac-
rophages. Compound 16 proved to be an exceptionally potent
inhibitor of the RTs carrying the K103N, Y181I, and L100I
mutations. These results suggest that, similar to EFV’s ana-
logues, IAS derivatives may successfully adopt the 4,5-
dihaloindole substitution pattern. Compound 16 is a very robust
lead compound for the development of new second-generation
NNRTIs that should be effective against the viral mutant strains
arising in patients whose viral loads rebounds after an initial
response to the drug.10 These results serve as basis for the design
of new IAS derivatives.
1
ethanol). H NMR (DMSO-d6): δ 1.30 (t, J ) 7.1 Hz, 3H), 2.14
(s, 3H), 4.29 (q, J ) 7.1 Hz, 2H), 7.38 (dd, J ) 2.2 and 8.9 H z,
1H), 7.54 (d, J ) 8.9 Hz, 1H), 7.59 (d, J ) 2.2 Hz, 1H), 12.3 ppm
(broad s, disappeared on treatment with D2O, 1H). IR (nujol): ν
760, 850, 1110, 1160, 1290, 1660, 3200 cm-1
.
From 2,4-Dichlophenylhydrazine. A mixture of 2,4-dichlo-
rophenylhydrazine (13.3 g, 0.075 mol), ethyl pyruvate (13.9 g, 10.3
mL, 0.12 mol), glacial acetic acid (0.9 mL), and absolute ethanol
(105 mL) was refluxed for 2 h. After the mixture was cooled at
room temperature, the solid was filtered and recrystallized from
ethanol to afford 18 (17.1 g, 83%). The melting point and spectral
data were identical to those of the sample prepared from 2,4-
dichloroaniline.
General Procedure for the Synthesis of Derivatives 24-31.
Example. Ethyl 5,7-Dichloro-1H-indole-2-carboxylate (24). Com-
pound 18 (16.5 g, 0.06 mol) was added by portions to PPA (165
g) preheated at 110 °C. The mixture was stirred at 110 °C for 30
min and then quenched on ice-water. The solid was filtered,
washed with water, and dried. The crude product was purified by
silica gel column chromatography (chloroform as eluent) to give
24 (5.0 g, 37%), mp 143-145 °C (from ethanol). 1H NMR (DMSO-
d6): δ 1.31 (t, J ) 7.2 Hz, 3H), 4.37 (q, J ) 7.2 Hz, 2H), 7.23 (s,
1H), 7.45 (d, J ) 1.5 Hz, 1H), 7.76 (d, J ) 1.5 Hz, 1H), 12.4 ppm
(broad s, 1H, disappeared on treatment with D2O). IR (nujol): ν
Experimental Section
Chemistry. Melting points (mp) were determined on a Bu¨chi
510 apparatus and are uncorrected. Infrared spectra (IR) were run
on Perkin-Elmer 1310 and SpectrumOne spectrophotometers. Band
position and absorption ranges are given in cm-1. Proton nuclear
magnetic resonance (1H NMR) spectra were recorded on Bruker
AM-200 (200 MHz) and Bruker Avance 400 (400 MHz) FT
spectrometers in the indicated solvent. Chemical shifts are expressed
in δ units (ppm) from tetramethylsilane. Chromatography columns
were packed with Merck alumina (70-230 mesh) and Merck silica
gel (70-230 mesh). Aluminum oxide TLC cards from Fluka
(aluminum oxide precoated aluminum cards with fluorescent
indicator at 254 nm) and silica gel TLC cards from Fluka (silica
gel precoated aluminum cards with fluorescent indicator at 254 nm)
were used for thin layer chromatography (TLC). Developed plates
were visualized by a Spectroline ENF 260C/F UV apparatus.
Organic solutions were dried over anhydrous sodium sulfate.
Concentration and evaporation of the solvent after reaction were
carried out on a Bu¨chi Rotavapor R-210 equipped with a Bu¨chi
V-850 vacuum controller and Bu¨chi V-700 and V-710 vacuum
pumps. Elemental analysis results were within (0.4% of the
theoretical values.
General Procedure for the Synthesis of Derivatives 6-17.
Example. 5,6-Dichloro-3-(phenylsulfonyl)-1H-indole-2-carboxa-
mide (6). Compound 44 (0.56 g, 0.0014 mol) was heated at 100 °C
with 30% ammonium hydroxide (25 mL) and ammonium chloride
(40 mg) in a sealed tube overnight. After cooling, the reaction
mixture was poured on ice-water, stirred for 15 min, and extracted
with ethyl acetate. The organic layer was washed with brine and
dried, and the solvent was evaporated. The crude residue was
purified by silica gel column chromatography (95:5 chloroform-
ethanol as eluent) to afford 6 (0.45 g, 87%), mp 292-295 °C (from
ethanol). 1H NMR (DMSO-d6): δ 7.58 (m, 3H), 7.76 (s, 1H), 8.06
(m, 2H), 8.17 (s, 1H), 8.32 (broad s, 1H, disappeared on treatment
with D2O), 8.50 (broad s, 1H, disappeared on treatment with D2O),
13.17 ppm (broad s, 1H, disappeared on treatment with D2O). IR
(nujol): ν1130,1280,1660,3100,3300cm-1.Anal.(C15H10Cl2N2O3S
(369.22)) C, H, N, Cl, S.
1000, 1180, 1240, 1300, 1680, 3240 cm-1
.
General Procedure for the Synthesis of Derivatives 32-43.
Example. Ethyl 5,6-Dichloro-3-(phenylthio)-1H-indole-2-car-
boxylate (32). Boron trifluoride diethyl etherate (0.28 g, 0.24 mL,
0.002 mol) was added under a dry argon atmosphere to a mixture
of 23 (1.54 g, 0.006 mol), N-(phenylthio)succinimide11 (1.37 g,
0.0066 mol), and anhydrous dichloromethane (40 mL). After the
mixture was stirred at room temperature for 2 h, boron trifluoride
diethyl etherate (0.56 g, 0.48 mL, 0.004 mol) was added and the
mixture was heated at 45 °C for 2 h. After cooling, the mixture
was diluted with chloroform and brine while shaking. The organic
layer was separated, washed with sodium hydrogen carbonate
solution and brine, and dried. Removal of the solvent afforded 32
(2.17 g, 96%), mp 192-195 °C (from ethanol). 1H NMR (DMSO-
d6): δ 1.25 (t, J ) 6.9 Hz, 3H), 4.34 (q, J ) 6.9 Hz, 2H), 7.10-
7.33 (m, 5H), 7.55 (s, 1H), 7.74 ppm (s,1H). IR (nujol): ν 700,
1240, 1660, 3210 cm-1
.
General Procedure for the Synthesis of Derivatives 44-55.
Example. Ethyl 5,6-Dichloro-3-(phenylsulfonyl)-1H-indole-2-
carboxylate (44). 3-Chloroperoxybenzoic acid (0.87 g, 0.005 mol)
was added to an ice solution of 32 (0.62 g, 0.0017 mol) in
chloroform (30 mL). The mixture was stirred at room temperature
for 1.5 h and then poured on crushed ice and extracted with
chloroform. The organic solution was shaken with sodium hydrogen
carbonate solution and brine and dried. After concentration to a
small volume, the solution was passed through an alumina column
chromatography (ethyl acetate as eluent) to furnish 44 (0.55 g, 82%),
mp 196-197 °C (from aqueous ethanol). 1H NMR (DMSO-d6): δ
1.30 (t, J ) 7.1 Hz, 3H), 4.43 (q, J ) 7.1 Hz, 2H), 7.61 (m, 3H),
7.85 (s, 1H), 8.06 (m, 2H), 8.47 ppm (s, 1H). IR (nujol): ν 700,
840, 1120, 1280, 1700, 3500 cm-1
.
General Procedure for the Synthesis of Derivatives 18-22.
Example. Ethyl Pyruvate 2,4-Dichlorophenylhydrazone (18).
From 2,4-Dichloroaniline. A solution of sodium nitrite (11.2 g,
0.16 mol) in water (14.7 mL) was dropped onto an ice-cooled
Acknowledgment. We are thankful for the financial support
of the Italian MUR (PRIN 2006, Grant 2006030809) and Istituto
PasteursFondazione Cenci Bolognetti.